When a Concorde disappears, the Doctor discovers that it has been
hijacked back through time to the Pleistocene Era. Arriving there, he,
Nyssa and Tegan find that Concorde's crew and passengers have been
enslaved by the sinister Kalid, who is forcing them to excavate a
sanctum within a mysterious citadel. Entombed within is the
consciousness of a gestalt race called the Xeraphin, who possess
devastating mental powers. The Doctor learns that Kalid is really the
Master, who plans to harness the evil side of the Xeraphin in order to
wreak havoc throughout the cosmos.

Production

By 1979, Peter Grimwade was no stranger to Doctor Who. Grimwade
had worked on the programme as a production assistant as far back as Spearhead From Space in 1970. Over the course
of the intervening decade, he began amassing experience as a
scriptwriter, contributing to Z Cars, and latterly completed the
BBC's internal directors course. Around this time, Grimwade approached
Doctor Who script editor Douglas Adams with an idea for the
programme, concerning an evil force which came to control a rogue
element amongst an alien species.

The concept was relayed to Adams' successor, Christopher H Bidmead, who
was intrigued and embarked upon further discussions with Grimwade.
During one such meeting, the pair ran an errand at Heathrow Airport,
which inspired the notion of involving Concorde -- the world's first
commercial supersonic aircraft, which had only been in service for four
years at that point -- in Grimwade's adventure. Bidmead thought that
this would be a nice way to bridge the writer's fantastical notions with
reality, while Grimwade himself hoped it might lead to a chance to ride
aboard Concorde. Soon thereafter, on March 14th, 1980, Grimwade was
commissioned to produce a storyline under the title
“Zanadin” -- a name which had been conceived by Grimwade,
Bidmead and producer John Nathan-Turner to be intentionally bizarre.

Doctor Who was the first TV
drama to gain access to both Heathrow Airport and a British Airways
Concorde for filming

Grimwade worked quickly on his outline, and consideration was given to
positioning the story (now renamed “Xeraphin”) as the finale
of Doctor Who's eighteenth season. At about this time, however,
Nathan-Turner decided to hire Grimwade to direct another Doctor
Who adventure, Full Circle, delaying
work on “Xeraphin”. It was subsequently agreed that Grimwade
would revisit his adventure at the end of the summer -- after completing
Full Circle and before directing another
Doctor Who serial, Logopolis -- with
a view to making “Xeraphin” as part of Season Nineteen.

The postponement of “Xeraphin” was beneficial in at least
one respect, because it gave Nathan-Turner more time to negotiate access
to both Heathrow Airport and a British Airways Concorde for filming --
both firsts for a television drama. Aided by false intimations that the
Doctor Who production office was in discussions with Air France
for similar accommodations, Nathan-Turner scored a major coup when he
was able to obtain the necessary permissions from both Heathrow and
British Airways.

As 1980 wore on, it became clear that Grimwade would have to make
several changes to his storyline. Tom Baker had now decided to leave
Doctor Who, and so “Xeraphin” would feature an
entirely different line-up of Doctor and companions. In addition,
Nathan-Turner and Bidmead had reintroduced the Doctor's Time Lord
archnemesis, the Master, and the producer was eager to feature the
character in two stories every year. It was planned that the Master
would appear in Season Nineteen's debut serial, and Nathan-Turner asked
Grimwade to incorporate the character into “Xeraphin” as
well. With the storyline duly amended, Grimwade was formally
commissioned to script his adventure on September 22nd. The contract was
issued under the title “Zanadin”, but the story reverted
back to “Xeraphin” soon thereafter.

More changes came over the course of 1981. It had been decided that
Adric would be dropped as a companion in the story preceding
“Xeraphin”, and so would have to be removed from the action.
Furthermore, since “Xeraphin” was now intended to be the
last story of Season Nineteen, Nathan-Turner wanted to end the year on
something of a cliffhanger, akin to the Doctor's regeneration at the
conclusion of Logopolis. It was agreed that
“Xeraphin” should culminate with Tegan apparently being left
behind as the Doctor and Nyssa leave in the TARDIS. There were no plans
to write Janet Fielding out of Doctor Who, but this development
would also give Nathan-Turner the ability to change his mind about
retaining Tegan as recording for Season Nineteen progressed. Meanwhile,
new script editor Eric Saward felt that the Master had worn out his
welcome and championed the idea of killing him off in
“Xeraphin”. Nathan-Turner, however, stood by his plan to
feature the Master as a recurring foe for the foreseeable future.

Eric Saward championed the idea of killing off the Master
in Time-Flight

During the summer, the job of directing “Xeraphin” -- now
classified as Serial 6C -- was offered to Andrew Morgan, whose credits
included Blake's 7. Unfortunately, Morgan was unimpressed by
Grimwade's scripts, and turned down the offer at the last minute. Left
with little time to find a replacement, Nathan-Turner turned to Ron
Jones, a neophyte director who was just competing Black Orchid, his first assignment. Jones
agreed to move directly onto “Xeraphin”. Meanwhile, both of
Grimwade's Concorde captains had to be renamed to avoid confusion with
real individuals: Irving became Markham and then Urquhart, while
Rathbone became Stapley. Flight Engineer Tulley was subsequently
rechristened Scobie as well.

Anthony Ainley was contracted to play the Master on October 1st. It was
agreed that he would be credited as “Leon Ny Taiy” (an
anagram of “Tony Ainley”) at the end of part one, in order
to preserve the surprise of Kalid's unmasking in the second installment.
It was also observed that the death of Adric in the preceding story, Earthshock, might be spoiled if advance
listings for Serial 6C omitted Matthew Waterhouse's name. Consequently,
a brief appearance by an illusory Adric was added to episode two.
Meanwhile, the novelty of the strange title “Xeraphin” had
gradually worn off on the production team, and in mid-December, the
story was renamed Time-Flight.

Heathrow Airport in Hounslow, Middlesex was the only location used for
Time-Flight. Work there began on January 6th, 1982, with material
on the concourse shot in Terminal One. The next day, cast and crew
shifted to the roof of Terminal Three; by this stage, Fielding had been
reassured that Tegan was coming back in Season Twenty, and indeed this
decision had been made as far back as September. Waterhouse was issued a
contract for his cameo appearance on this day. Work at Heathrow was
intended to conclude on the 8th, but the weather was stormy and the
Concorde which British Airways had planned to provide had to be pressed
into service. As a result, scenes in Concorde and on the tarmac were
postponed to January 11th, at the British Airways Maintenance Area.

Jones had hoped that some of the scenes on the prehistoric heath might
be filmed on location or at the Ealing Television Film Studios, and was
disappointed to learn that the budget for Time-Flight would not
permit this. In the event, the heath was the main concern during the
serial's first studio block on January 19th and 20th in BBC Television
Centre Studio 8. Originally, this work was intended to be confined to
the first day, but technical problems pushed some scenes back to the
20th. It was then a race to complete the other planned shots -- in and
around the Heathrow offices, as well as various special effects.
Nathan-Turner was dissatisfied with the results, and some of the
material was remounted in TC8 on January 24th.

On February 2nd, Matthew Waterhouse returned to finish out
his tenure on Doctor Who

Meanwhile, it had been discovered that the script for part three was
drastically short, and on the 25th, Saward asked Grimwade to contribute
a further seven minutes for the episode. Later that week, Grimwade
provided various new and extended scenes, including more material
involving Bilton and Stapley spying on the Master and later trying to
pilot the TARDIS, and additional exposition about the Xeraphin.

The second studio block -- again in TC8 -- spanned February 1st to 3rd.
The initial day concentrated on TARDIS material. The 2nd was devoted to
scenes in the Concorde hold, the area outside the sanctum, and the
various corridors of the citadel. Waterhouse returned on this day to
finish out his tenure on Doctor Who, more than two months after
recording his farewell adventure. Waterhouse concentrated on the theatre
after leaving Doctor Who, although he had a small role in a 1984
science-fiction film called The Killing Edge and recorded a cameo
appearance as Adric in Peter Davison's final story, The Caves Of Androzani. Waterhouse's first
novel, Fates, Flowers, was self-published in 2006.

February 3rd was the final day of filming for both Time-Flight
and Doctor Who's nineteenth production block. The material that
remained to be recorded included the sequences in Kalid's chamber, as
well as the Xeraphin sanctum. The transmission of Time-Flight
episode four then brought Doctor Who's nineteenth season to a
close on March 30th.